A systematic review of studies measuring health-related quality of life of general injury populations: update 2010–2018

A new search of empirical studies on the HRQL of general injury populations was conducted. The search strategy that was developed for the systematic review of Polinder et al. [12] was updated in collaboration with a librarian specialising in literature searches. In order to match the database specific indexing terms, the search strategy was adjusted for the different electronic databases: Embase, PubMed (Medline Ovid), Web of Science and PsycINFO. The terms used in the search strategy were: ‘quality of life’ and ‘health related quality of life’, ‘functional status assessment’, ‘injury’ and ‘trauma’, and ‘cohort analysis’ (complete search strategy in Appendix 1). Articles were included in the search if the period of publication was between 2010 and 2018, and if they were peer-reviewed. The reference lists of the included articles were also screened, in order to detect additional articles that were relevant, and to identify important key terms. Details of the systematic review process were successfully registered and published within the PROSPERO database (registration number CRD42019120207).

To be included in this review, studies had to use a generic HRQL or disability measure at more than one time point in a population of injury/trauma patients. While HRQL and disability are unique constructs, the World Health Organization International Classification of Functioning, Disability and Health (ICF) acknowledges the relationship between disability and HRQL, particularly with respect to participation in activities of daily living [5]. For the purpose of this review, the World Health Organization (WHO) definition of disability is used. The WHO defines disability as an umbrella term reflecting impairments, activity limitations, and participation restrictions [18]. The concept of HRQL is more specific, reflecting an individual’s or population’s perceptions of health (mental and physical) and functional status [19]. Several measures of disability, such as the World Health Organization Disability Assessment Schedule (WHODAS) based on the ICF, can be used to evaluate not only disability but also HRQL [20].

Additional inclusion criteria were publication in English and in a peer-reviewed journal between 2010 and 2018. Studies that focused on only one specific injury population, such as traumatic brain injury patients, were excluded as only studies with a general injury population were the focus of this review. Furthermore, studies measuring HRQL in people other than individuals with injury were excluded, as were studies employing non-generic HRQL instruments, and review and pilot studies. There was no restriction on age or injury severity. Therefore, studies focusing on a specific age group or specific injury severity, but not focusing on a specific injury, were included.

After completion of the database searches, relevant articles were selected in three steps. First, the titles of the articles were screened, next, the abstracts of the articles selected in step one were screened, and finally, the entire articles selected in step two were read. By screening the titles, abstracts and articles, it was determined whether an article should be included or not according to the selection criteria. The screening procedure was conducted by two researchers independently (AG and AR). In cases of disagreement between the two researchers, a third researcher (JH) was consulted. This researcher also checked a sample of abstracts (n = 50) in order to quality assure the process. The full articles that were eligible for inclusion were then analysed by two reviewers (AG and AR), using a modified version of the data extraction form developed for the original review by Polinder et al. [12]

The methodological quality of each study was independently assessed by two researchers (AG and AR) using three items from the RTI Item Bank on Risk of Bias and Precision of Observational Studies [21]. This item bank consists of 29 items designed to evaluate the quality of observational studies of interventions or exposures. It is recommended to select items that can evaluate the most critical threats to validity associated with the studies under investigation. For this review, items 16, 17, and 18 were selected for use; each of these items address potential bias associated with follow-up assessments in longitudinal studies. In addition, alignment of studies with the Guidelines for the Conduction of Follow-up Studies Measuring Injury-Related Disability was analyzed [16].

The results of all studies were tabulated in order to identify the different measures used, the methods of reporting HRQL information (e.g. summary scores), and whether any changes in HRQL over time were observed. For studies presenting HRQL summary scores, the scores could range from either 0 to 1 or 0 to 100 depending on the measurement instrument used. Two examples of generic HRQL instruments that can be used to derive a summary score are the EQ-5D and the SF-36. With respect to disability, an example of an instrument that can be used to derive a summary score is the WHODAS II [22]. For all instruments examined, lower scores were representative of worse health.

The search strategy in the specified databases provided a total of 8152 unique potentially relevant articles (see Fig. 1). One additional article that did not turn up in our search was extracted from the reference list of an included study, and added to the relevant titles. In the first selection round, based on scanning the titles, 7386 articles were excluded. The main reasons for exclusion were that studies were not about injury or were about a specific injury type, rather than injury in general. The abstracts of the remaining 766 articles were read in the next selection round, resulting in the exclusion of 668 more articles due to a lack of HRQL measurement. The full texts of the remaining 98 articles were read, and led to the final inclusion of 44 articles. These articles represent 29 unique studies. The main reason for final exclusion of 54 articles was a lack of a sufficient HRQL measurement or the lack of multiple HRQL measurements.

Study characteristics are presented in Table 1. Out of the 44 articles that were included in our systematic review, most (n = 12) reported findings from a single prospective cohort study conducted in New Zealand [14, 27‐37]. Seven articles were published using data from Australia [24‐26, 39‐42], with two articles related to the same study cohort from Victoria [41, 42] and two articles related to the same cohort from South-East Queensland [25, 26]. Five articles reported on five unique studies conducted in the United States [38, 53, 57, 64, 65]. Three articles resulted from two studies in Switzerland [43‐45] and three articles resulted from two studies in Norway [59, 60, 62], respectively. Two articles from two different studies were detected from both Italy [46, 47] and Sweden [52, 56]. Remaining articles were from studies conducted in Hong Kong [55], India [48], British Colombia [58], Iran [23], Spain [50], United Kingdom [49], Thailand [63], Japan [61] and Vietnam [51] (all n = 1). One study was a multicentre study, conducted in both Australia and Hong Kong [54]. The sample sizes for each investigation ranged from 105 to 87,134, with the majority of the samples in the range of 105 to 668 participants (n = 28). Four studies measured HRQL in children and adolescents [48, 53, 57, 58], while all other studies focussed on adult populations. All studies included a non-specific injury population, with differing injury severities.

Approximately a third (n = 10) of all studies focused on all injury severities, with a main inclusion criteria of hospital admission or injuries likely to result in insurance claims for more than just medical treatment. The second largest group of studies focussed on major injuries (n = 18). Inclusion criteria were varying, with some studies only requiring ≥24 h stay at the hospital or admission to intensive care unit (ICU) (n = 7), and other studies requiring a minimum score on the ISS (Injury Severity Score) or NISS (New Injury Severity Score). ISS for major injuries ranged from ISS > 12 (n = 2) to ISS ≥16 (n = 2), versus NISS ranging from NISS ≥8 (n = 1) to NISS ≥16 (n = 2). The remaining 5 studies focused on moderate (n = 3) or mild to moderate (n = 2) injuries, with moderate injury studies requiring AIS (Abbreviated Injury Scale) ≥2 (n = 1) or ISS ≥9 (n = 2), and mild to moderate injury studies requiring ISS < 15 (n = 1) and length of hospitalisation < 24 h (n = 1).

All studies that were included in this review were prospective cohort studies. Seven out of the 29 unique studies were multicentre studies [24, 48, 49, 52, 54‐56]. Across studies HRQL and disability were measured with 14 different measurement instruments. Generic instruments SF-36 (n = 13) and EQ-5D (n = 7) were most commonly used, followed by SF-12 (n = 6) and GOSE (n = 4), as can be retrieved from Fig. 2. Approximately 45% of the studies (n = 13) used more than one measurement instrument, of which 10 used two instruments, and 3 used more than two instruments. All measurement instruments were generic, with three out of four studies in children using a child-specific instrument (PedsQL; PedsQL 4.0; PedsQL infant scales) only, and one study in children using two all ages instruments (SF-12 and SF-36). Measurement of HRQL was conducted at different time points in studies, with the number of follow-up points varying from one (n = 4) to five (n = 3). HRQL was assessed at more than one follow-up point in 25 studies, with measurement at 6 and 12 months most frequent across all studies (n = 14 and n = 19, respectively) (Fig. 3). Three other common measurement points were 24 months (n = 12), 1 month (n = 9) and 3 months (n = 7) after injury. Studies used different administration methods of questionnaires, with telephone interview as the most common method (n = 13). A combination of different methods was common, with baseline measurement often performed in a face-to-face interview, and later follow-up measurements done by either telephone or postal/email interview.

Length of follow-up was consistent for all study participants in all but two studies [25, 26, 56]. The same results were found regarding whether follow-up time was sufficient for measuring primary outcomes, with only two studies reporting an insufficient follow-up period [24, 47]. However, attrition appeared to be a problem in many studies: 18 out of 29 studies exceeded the attrition norm of 20% for < 1 year follow-up and 30% for ≥1 year follow-up.

Regarding adherence to the Guidelines for the Conduction of Follow-up Studies Measuring Injury-Related Disability, it was found that study populations were generally in accordance with the guidelines. However, measurement in respondents with mental and/or social problems was only specifically mentioned in two studies [40, 48], whereas all other studies provided no or unclear information on the subject. Even though the guidelines recommend a combination of the EQ-5D and HUI3 to measure HRQL, none of the included studies used this combination. The EQ-5D and HUI3 were used separately in a number of studies [14, 30‐35, 39, 42‐45, 49‐51]. Six studies complied to the measurement points required by the guidelines, namely one, two, four and 12 months after injury [48, 49, 51, 58, 64, 65]. Even though other studies did not follow all required measurement points, the majority complied with at least one.

Recovery patterns of HRQL after injury were found to differ across subgroups in most studies. There was substantial variation in the predictors of HRQL after injury, however, seven predictors were mentioned in six or more articles: age (n = 14), gender (n = 12), pre-injury health status (n = 12), hospitalisation status (n = 7), nature of injury (n = 7), injury severity (n = 7) and socio-economic status (n = 6). Older age and female gender were found to have a negative impact on the outcome of HRQL after trauma in several articles [24, 31, 41, 47, 50, 51], whereas in two other articles male gender was found to have a negative association with HRQL [45, 55].

Studies that reported HRQL values generally reported improvements in HRQL over time (see Table 1). However, not all studies that were included reported specific outcomes of HRQL, as some studies reported on odds ratio and relative risks. Improvement in HRQL was found in all studies, however, pre-injury status or population level was not reached for the total injury population after 6–24 months [24, 26, 31, 36, 44, 46, 47, 49, 55, 60, 62]. Figures 4 and 5 summarise HRQL scores of all articles that provided a mean HRQL score at 12 months after injury. Some articles provided mean scores only per subgroup, and have therefore been included in the figure for each subgroup. Figure 4 shows the physical component score (PCS) and mental component score (MCS) for both SF-12 and SF-36, whereas Fig. 5 shows the summary score for the EQ-5D, EQ-VAS, HUI3 and PedsQL (4.0).